Pleasing pepper perfumes: Semiochemical attractants for pepper weevil management

Pepper weevils are the most serious pests of cultivated pepper varieties (Capsicum spp.) throughout several northern and southern US states, Central America, the Caribbean and Canada. While weevil feeding severely reduces yield, feeding by female weevils also induces pepper plants to release volatiles which are highly attractive to males and females. The objectives of this study were to determine the behaviorally attractive fractions of pepper headspace extracts using a Y-tube olfactometer; identify specific compounds from those attractive fractions using coupled gas chromatography-electroantennographic detection (GC-EAD); and determine the optimum dose for the active compounds. Extracts of headspace volatiles from fruiting jalapeno plants fed on by female weevils were tested in Y-tube olfactometer experiments and shown to be as attractive as intact damaged plants. Headspace extracts fractionated by preparative gas chromatography and tested in Y-tube behavioral assays revealed that fractions containing green leafy volatiles (GLV) and sesquiterpenes were most attractive to male and female weevils. GC-EAD analyses revealed 17 peaks which elicited antennal responses from both male and female weevils. The majority of these peaks were found in the behaviorally active GLV and sesquiterpene fractions. The EAD active compounds were identified using GC/MS and further GC-EAD dose-response experiments with synthetic forms of the active compounds showed significant and sex-specific dose effects for males and females. Knowledge of a minimum suite of attractive compounds formulated at an optimum dose will help to facilitate the development of an effective semiochemical strategy for pepper weevil management.